Wet scrubbers have been proven to be very effective in cleaning waste gas streams from a variety of sources, including toxic waste incinerators. Such incinerators are used in many applications as, for example, in hospitals where the incinerators are utilized for convenient disposal of a large variety of substances. After incineration, many potentially hazardous and toxic constituents pass, in an gas stream, from the incinerator into a wet scrubber for cleaning purposes, prior to discharge to the atmosphere. The wet scrubber removes a substantial amount of the unwanted constituents from the gas stream, prior to discharging the clean gas into the atmosphere. The particulate matter is removed from the scrubber in the form of a sludge, and contains many unwanted and potentially toxic constituents, generally entrained in an aqueous medium. While the clean gas may be released into the atmosphere in a convenient manner, safe disposal of the sludge is an important consideration.
Traditionally, sludge disposal has presented a considerable problem. The problem is even more serious when the sludge contains such substances as heavy metals, dioxin and natural and synthetic organic compounds having health threatening characteristics. In the past, before environmental and health concerns were focused on matters such as sludge disposal, the disposal of sludge from wet scrubbers was less of a problem. Of course, improper disposal methods, while convenient, could impose a significant penalty on the environment. Such methods also present a safety problem for those persons responsible for the handling of the toxic sludge. Thus, such sludge disposal has presented an unacceptable public health hazard. Alternative methods of handling unwanted constituents in waste gases have been employed. In this regard, reference may be made to U.S. Pat. Nos. 3,590,918; 4,013,455 and 4,133,654.
In general, conventional systems, such as the one disclosed in U.S. Pat. No. 4,013,455, have attempted to dry the discharged sludge to help facilitate safer removal thereof. In this regard, the sludge is dried to remove water from the sludge, to leave a relatively dry particulate. However, a limitation of such a technique is that, when the sludge drying equipment is utilized in conjunction with an operating scrubber system, the drying equipment can slow down the scrubbing operation. In addition, if a malfunction in the drying equipment occurs, the entire scrubber operation may be interfered with, or even curtailed. The scrubber may require to be shut down until repairs are made. Thus, it would be highly desirable to have a waste particle disposal system which is capable of efficient particle removal, without substantial interference with the associated wet scrubber.
In U.S. Pat. No. 4,013,455, there is disclosed a process in which sludge, from a wet scrubbing process is flash evaporated, utilizing incinerator waste gas, to dry the sludge. Although the weight and volume of the sludge mass is reduced by the evaporation of water therefrom, the resultant mass of particles can still present serious handling and disposal problems, especially where the system is employed in a facility, such as a hospital, where safety and sanitary conditions are of the utmost importance.
As an illustration of the problems presented in disposal of dried sludge, the products generated from a typical hospital incinerator may deserve some attention. In these cases, the dry particle mass can include highly toxic materials such as heavy metals and dioxin. As mentioned, water removal from the sludge has some benefit by reducing the weight and volume of the material requiring disposal. However, substantial problems relating to handling and disposing of the noxious dry particulate mass remain.
In general, hospitals or other such institutions and organizations are found in highly populated urban centers. As a result, dry particulate waste substances should be handled very carefully, by highly trained and well paid personnel, to avoid contamination of residential neighborhoods. In addition, practices must be implemented to prevent particles from becoming airborne, thereby presenting a public health hazard. Of course, the needs of the patients and other people, such as employees of the hospital, must be considered in this regard. Because of their often weakened physical condition, patients should be shielded or otherwise protected from exposure to health threatening airborne particles. Thus, the problem of waste substance handling, especially in the hospital environment, becomes an expensive, undesirable and unwanted task.
Even when safe and efficient waste handling techniques can be utilized, disposal of the dry particulate waste can present a serious problem, from the ecological and economic viewpoint. It is well recognized that landfills and other areas for receiving toxic waste disposal are being depleted at a rapid rate. As a result, it can be necessary, in some situations, to haul toxic substances for long distances, away from populated centers, for disposal purposes. Such transportation expenses can add unwanted expense to the waste disposal process. In addition, the danger of contamination of the environment can become more significant as the amount of expert and skillful handling is required, and the distance of transportation to a disposal site increases.
In view of the foregoing, it would be highly desirable to have an apparatus and method for disposing of noxious, unwanted particulate substances, in a safe and efficient manner. Such an apparatus and method would permit accumulation of unwanted particulates in a safe and convenient manner, by relatively untrained personnel. In addition, it would be especially advantageous if the noxious particulate could be disposed of conveniently without the necessity of transporting the product over excessive distances, to waste disposal sites.